There is a projection device that superimposes and displays an image on a scenery seen by a driver by causing the image to be transparently displayed on a projection surface such as windshield. In recent years, with the use of the projection device, a vehicle device that supports driving by, for example, indicating a route direction at a complicated intersection by an arrow according to a road actually traveling, or framing a road sign so as to urge a driver to pay attention has also emerged.
Meanwhile, a position of a driver's face is not necessarily located at a fixed position. For that reason, depending on the position of the driver's face, the superimposed and displayed image may be displayed with deviation from a real scenery, and advantages of the projection device displaying the image on the real scenery in a superimposed manner cannot be utilized in some cases. Also, the display of the image at a deviated position may cause the driver to misunderstand. For that reason, for example, Patent Literature 1 has proposed that a method for displaying the image is devised to alleviate an image shift caused by the driver's viewpoint position.